Netgraph plot disappears

[barun-saha]

When I execute a netgraph example as a Python script, the plot window appears and disappears almost instantly. However, when I execute each line of code in the Python prompt, the plot window stays.

An MWE:

import numpy as np
import matplotlib.pyplot as plt; plt.ion()
import netgraph

graph = [
(0, 1),
(1, 2),
(2, 0)
]

netgraph.draw(graph, node_labels={0: '0', 1: '1', 2: '2'})

The same problem occurs with networkx directed graphs as well.

[paulbrodersen]

Hi Barun

What you describe is expected behavior for any python script: once the script terminates, the python process (and any child process thereof) is killed.

So what is happening in your MWE:

1. You run the script, i.e. a python process is created which evaluates your script line-by-line, and the figure is created. Figure creation spawns a child process that displays the rendered image.
2. As you are in interactive mode (plt.ion()), figure creation is non-blocking, i.e. the rest of the script is evaluated until you reach the end of file.
3. At this point, the python parent process is terminated. The OS realizes that the figure is in an orphan child process and kills it as well.

Solution: don't use interactive mode, and force the figure display with plt.show() after netgraph.draw() or equivalent.

Hope that helps.

Best,
Paul